Dead Speedo and now flashing SES

[Magikal]

ok..1990 Beretta 3.1 engine 5spd manual trans.      

just a couple days ago the speedo started not working intermittenly and suddenly this evening the SES light is flashing quite fast, not like in the diagnostics mode, much faster.   no pattern.   are these related?   what are they?  please help.

[docrodg]

Could be seperate issues, or you have an electrical problem, not enough juice.  Check the alternator out and see if it is putting out enough.  Run an ABS diagnostics for a code and check the pulse on the speedo (a multimeter with a hertz function will do it).  It is possible they are also related by a bad wheel sensor or two... giving a bad signal to the speedo and the abs making it think that the wheel is locked up.  when the ABS is active it will flash so if it thinks you have a locked up wheel you will get that flashing without pattern as it senses a wheel move then stop.  Easy way to sheck those is a hertz reading while spinning the wheel or better an oscilloscope.

[Jeff P]

The speedo problem could be caused by the Vehicle Speed Sensor in the transmission, or both problems could be caused by a bad ECM...Try tapping on the ECM with the handle of a screwdriver while the engine is running and see if it stumbles or anything.  If you can, find a spare ECM from the same year/transmission to swap in for testing.  Luckily, since yours is a '90, you don't have to worry about ABS problems.

[Magikal]

Ok...my bad...I totally forgot when I posted the original message that I had added an inline SuperChip module (fits inbetween the EPROM and ECM).   It has been very hot here (upper 90's low 100's with 0% humidity) for weeks now.   Well the other day the car suddenly would die while driving highway speed.  I would pull over, switch the key off and then back on (it would start) and it would run fine.  This happened 4 times in like 40 miles perhaps.   I immediately suspected computer issues and in order to keep it simple I decided to remove the Superchip module for diagnostics, etc.   After removing the Superchip and going back to stock, all my problems were fixed, including the speedo.   No codes now, no flashing SES light, all good...that was 3 days ago and I have put several hundred miles on it with no problems.  

Stupid Computers!!  Guess the heat killed the chip.   Just my luck but I am glad it was such an easy fix.   I have just recently replaced the ECM and EPROM both.